A longitudinal fissure. Cleft lip (cheiloschisis, hare lip) is a cleft deformity of the upper lip which may be unilateral or bilateral. Unilateral clefts occur most commonly on the left side. It results from the failure of fusion of the embryonic maxillary and medial nasal processes around the fifth to sixth week of intrauterine life. A cleft palate occurs where there is failure in the fusion of the palatal shelves.
The cause of both conditions is multifactorial and can include environmental factors that affect the foetus, a genetic disposition, and drugs such as vitamin A and heroin (cocaine). In some cases a cleft may occur as part of a syndrome, such as a small mandible, and in others it may occur on its own. Cleft lip/palate is one of the most common congenital abnormalities, occurring in about 1:700 live births in the UK. Early diagnosis can now more readily be achieved using ultrasonic scanning. Treatment is surgical and the use of intra-oral plates in babies to minimize the extent of surgical intervention is controversial. A gingival cleft is a vertical fissure in the gingiva. A Stillman's cleft [P. R. Stillman (1871–1945), American periodontologist] is a narrow slit-like or triangular-shaped fissure of the gingival tissue extending from the gingival margin. It may be associated with trauma but is not necessarily diagnostic of occlusal trauma; it can often progress to more extensive gingival recession: the cleft may be associated with a bony dehiscence. A transverse cleft is an area of destruction caused by bacterial action in carious dentine which lies at right angles to the dentinal tubules.
Cleft lip and palate